For five months, delays in the launch of space shuttle Discovery almost made it look as if the orbiter was balking at prospect of making its final trip into space. Now, mission managers are contemplating extending the mission for yet another day beyond the one-day extension they've already approved.
With only two launches left in the shuttle program after Discovery and its six-member crew land next week, NASA is trying to ensure that each mission leaves the International Space Station with fewer and fewer immediate maintenance and clean-the-construction-site tasks for the station crew to deal with.
Time spent outside the station – which requires setting up space suits, an overnight "camp out" inside the airlock for spacewalkers, and crew members manning the station's robotic arm if heavy lifting is required – takes crew members away from other tasks, including experiments scientists have sent up to the station. And the shuttle crew represents six extra pairs of hands to unload and stow nearly 10,000 pounds of cargo Discovery lofted. Extending Discovery's visit by two days, rather than one, will help "get the ISS into the best possible configuration" before the shuttle leaves, says Royce Renfrew, the station's lead flight director. Japan's unmanned cargo carrier, loaded with refuse and packing material no longer needed, is also set to depart the station.
During the first spacewalk, conducted Monday, the duo performed a range of tasks, including preparations that cleared the way for their colleagues to install a fully packed, pressurized storage module on Tuesday.
Wednesday's spacewalk aimed to tackle what Kenneth Todd, who heads the space station's mission management team, dubbed "a lot of cats and dogs" –small jobs that would tidy up loose ends from previous spacewalks as well as prepare a borked cooling pump for its return to Earth. During both spacewalks, Bowen and Drew completed the major tasks for each event, then burrowed deeply into a pile of "get-ahead" tasks that would shrink the "to do" list for future spacewalkers.
Wednesday's outing ended 16 minutes earlier than planned, however, after a lamp on Drew's helmet came loose. The lamp serves as a task light for astronauts working on the station and provides illumination for a wireless video camera on the helmet. Bowen tried to reattach the lamp, but in the end could only tether it. Drew headed to the airlock, where he waited while Bowen wrapped up a couple of additional quick tasks.
Compared with two spacewalks and a module installation, two additional days for astronauts to take on the role of movers "isn't as glamorous," Mr. Renfrew acknowledged. "But the remainder of the mission is just as important" in preparing the station for life after shuttles.
With all of the mission's main objectives complete, "I'm a happy flight director," Renfrew said.
So happy, in fact, that the crews of the station and shuttle will get a half day off on Thursday, following the midday meal. Then, offloading the new module and stowing the goods begin in earnest before Discovery undocks and swings once around the station so crewmembers can take photos of its new configuration. Then it has one final day orbiting before the craft and its crew reenter into Earth's atmosphere and enter the aerospace history books.